Floating roof drain



M3/7379 31953 E. E. MHCHAELS FLOTING ROOF DRAIN Filed April 24, 1.946

Patented July 17, 1951 OFFlCE FLOATING ROF DRAIN Ernest E. Michaels, Birmingham, Ala., assigner to Chicago Bridge & iron Company, a corporation of illinois Application A ril 24, 1946, Serial No. 664,679

2 Claims. l l

This invention relates to a drain for a floating roof tank or the like whereby water is drained from the roof when it reaches a certain predetermined depth on the roof.

In iloating roof tanks the roof oats on top of the stored liquid and rises and falls as the amounts of liquid are increased and decreased. When rain water falls on the rooic its weight decreases the buoyancy of the roof until the water is drained therefrom. Various means have been proposed for draining this water from the roof, but many of these have the disadvantage of permitting vapors to escape from the storage portion of the tank.

The drain shown and described herein is automatic in operation in that it only operates after a predetermined amount of water has collected on the roof. The drain is very simple in construction and may be easily removed for inspection. The new drain comprises broadly a buoyant member adapted to be immersed in the liquid contents of the tank and a valve seated in an opening in the roof and attached to the buoyant member and normally held closed by the buoyancy of the buoyant member. This valve is displaceable downward by a predetermined depth of water over it, suicient in weight to overcome the buoyancy of the buoyant member. The buoyant member and valves are preferably movable in a substantially vertical path, and are guided in their movements by a housing around the buoyant member and supported on the lower surface of the roof around the valve.

The invention will be described as related to the embodiment set out in the accompanying drawings. Of the drawings Fig. l is a vertical section through substantially the center of the drain and through a portion of the roof; Fig. 2 is a plan View of the drain; and Fig 3 is an elevation of an alternate type of buoyant member; and Fig. 4 is a plan view of the buoyant member of Fig. 3.

The valve shown in the accompanying drawings comprises a substantially circular plate li! adapted to be bolted over a circular hole il in the deck I2 of a iioating rcoi. In the plate til there is located an opening i3 having sides sloping inwardly and upwardly and normally closed by a valve lll. Beneath the valve lil there is located a spherical float i5 connected by a substantially vertical stem I@ to the valve it. Surrounding the float I5 is a cylindrical housing I'! of slightly greater diameter than the float. This housing has its top edge attached to the plate Ill around the valve I. The bottom of the housing I'I is normally closed by a flat plate I8 having an opening I9 therein. The plate I8 is attached to the housing I'I by means of bolts 20, and may be removed so that the float I5, stem 6, and valve Ifl may be removed downwardly through the bottom end of the housing I1.

The valve lil is provided with radial guides 2| on its bottom surface extending to points adjacent the housing Il. These guides serve to center the valve within the housing.

The roof of the oating roof tank is provided with pontoons 22.

As soon as a predetermined depth of water has collected on the roof and over the plate IU the weight of the water over the valve I4 causes the valve to be pushed downwardly against the buoyancy of the float I5. The water then ows through the opening I3 into the cylindrical housing Il' around the float I5 and out through the opening I9 in the bottom of the housing to the bottom of the tank. This causes the depth of water on the roof to be decreased until it is no longer suiiicient to hold the valve I4 open. At this point the buoyancy of the float I5 causes the valve Iii to again rise in the housing I'I until the opening S3 is again closed. As can be seen, the valve is entirely automatic in operation, and serves to keep the water on top o the roof at substantially a constant depth.

The predetermined depth of water on the roof depends upon the buoyancy of the float I5 and the area of the top surface of the valve I4. The buoyancy of the float equals wh1r1'2, where r is the radius of the top surface of the valve I4, h is the predetermined depth of water, and w is the weight oi a unit volume of water. When all dimensions are in inches w will equal 0.0362 lb.

As the plate l!) is held in position by bolts 23 and the entire drain is mounted on this plate the drain may be inserted and removed as a unit. A gasket 2li is provided between the plate I0 and the deck l2 in order to form a vapor-tight seal.

When the drain is rst put into operation the liquid level within the housing I'I will be at some point such as is indicated at 25. The liquid level on the outside of the housing I1 will be substantially the same until vapors form under the roof. This vapor pressure will then cause the liquid level on'the outside of the housing to be at some lower level as indicated at 26. Any type of vent means may be provided for venting the vapor when the vapor pressure exceeds a desired value.

AS the cylindrical housing l'I is always immersed in the stored liquid, vapor losses through the opening I3 While the roof is draining are limited to the small amount of vapor within the housing.

Figs. 3 and 4 show an alternate type of iioat. This float 21 is of cylindrical shape and may be used instead of the spherical oat I5. Any other type of float may be used if desired.

Although the plate I is shown and described as being circular it may be polygonal or any other desired shape. Similarly the valve I4 may have any desired shape and the iloat I5 need not be spherical or cylindrical but may be any other shape.

Having described my invention as related to the embodiments set out in the accompanying drawings, it is my intention that the invention be not limited by the details of description unless otherwise specied, but rather be construed broadly fwithin its spirit and scope as set out in the accompanying claims.

I claim:

1. In combination with a floating roof tank, a drain for the deck of the roof comprising a sump in the deck, said sump having an opening in its bottom located above the level of the liquid in the tank and opening to the space beneath the deck, a cylinder in vertical alignment and communication with said opening and extending substantially vertically downwardly from the sump and into the liquid in the tank, a valve beneath the opening and adapted to move upwardly to close the same, a float in the cylinder and a rod connecting the float and valve, said rod having a length greater than the distance between the valve and the liquid level whereby to immerse the float in the liquid to maintain constantly an upward pressure on the valve when the roof is floating in the liquid, said valve having a predetermined horizontal area exposed to liquid in the sump and said sump having a depth to entrap a sufficient head of drain water above said area to overcome said upward pressure and open the valve.

2. The drain of claim l in which said cylinder has a length greater than the combined length of the float and rod whereby said valve is moved downwardly away from the opening when the roof is not floating on liquid in the tank.

ERNEST E. MICHAELS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 419,845 Flannery Jan. 21, 1890 1,591,799 Tinapp July 6, 1926 1,757,142 Kramer June 24, 1930 2,071,530 Howard et al Feb. 23, 1937 2,108,945 Runge Feb. '22, 1938 2,315,023 Stevenson Mar. 30, 1943 

